1. Field of the Invention
The invention relates to a video composite signal demodulating method and system and, more particularly, to a three-dimensional video composite signal demodulating method and system capable of inhibiting pseudo-color noises.
2. Description of Related Art
As shown in FIG. 1, a composite signal has luminance and chroma signal. In the NTSC (National Television System Committee) system, the chroma signal has a center frequency at 3.58 MHz, and in the PAL (Phase Alternation Line) system, the chroma signal has a center frequency at 4.43 MHz. When a video decoder receives a video composite signal, it uses a separator to perform a Y/C separation to separate the video composite signal's luminance and chroma signals for next proceeding.
FIG. 2 shows a schematic diagram of a typical Y/C separator. As shown in FIG. 2, the separator has a notch filter and a band pass filter. The notch filter reduces the chroma signal to accordingly obtain the luminance signal. Similarly, the band pass filter obtains the chroma signal. Since the chroma signal combines the luminance signal by a 3.58 (NTSC) or 4.43 (PAL) MHz carrier for transmission and a high frequency component of the luminance occupies a spectrum the same as the chroma signal, a signal originated from the luminance signal can be erroneously regarded as the chroma signal, even though the notch filter and the band pass filter can separate the luminance signal and the chroma signal, resulting in producing serious cross-color effect. Similarly, a signal originated from the chroma signal can be erroneously regarded as the luminance signal, thereby producing serious cross-luminance effect.
To overcome the cross-color effect and the cross-luminance effect, typically, a comb filter is used. However, the comb filter can reduce the cross-color effect and the cross-luminance effect only in a single direction (in horizontal direction or vertical direction). Therefore, it is desirable to provide an improved three-dimensional video composite signal demodulating method and system to mitigate and/or obviate the aforementioned problems.